Why do modern communications use satellites?

There are basically two reasons: 1. If you use a ground antenna, it will be blocked by tall buildings, mountains, etc., resulting in limited antenna coverage; 2. Since the earth's surface is curved, the ground antenna can only cover a certain radius.

With satellites, the coverage is global, and three geosynchronous satellites can cover the whole world, regardless of the geographical topography.

Electromagnetic wave propagation is the only in this case with the least loss and interference, while it has the greatest coverage, and the satellite overall is less expensive and more stable than that of aviation aircraft. In fact, helium balloons can also be used, I don't know if you can apply for a patent, haha I am the first person to conceive of helium balloon communication.

The easiest: because the earth is round. You slowly understand it.

Satellite communications are used in television, fax, telegraph, and data.

The application field of satellite communication continues to expand, in addition to the financial, post, telecommunications, meteorological, and other departments, distance education, telemedicine, emergency disaster response, emergency communications, emergency television imitation vertical broadcasting, sea, land and air navigation, Internet network, television, etc. will be widely used.

The development of new satellite communication technologies is endless. For example, very small aperture antenna earth station (VSAT) systems, mobile satellite communication systems in medium and low orbits have received extensive attention and applications. Satellite communications are also an important part of the global information superhighway in the future.

It is known for its wide coverage and large communication capacity.

Satellite communication has a long communication distance, and the cost of building a station has nothing to do with distance, and it can be built except for the poles of the earth. Flexible networking, convenient for multiple access. Good mobility, stable and reliable quality of communication lines.

Communication frequency bandwidth, large transmission capacity, suitable for a variety of service transmission, can be spontaneously self-collected for monitoring.

The biggest feature of the satellite communication system is the multi-access working mode, and the commonly used multiple access modes include frequency division multiple access, time division multiple access, space division multiple access and code division multiple access, and various multiple access modes have their own characteristics. Satellite communication has the ability to constitute a wide area complex network topology, and the high power density and flexible multi-point beam capability of satellite communication are coupled with on-board switching processing technology.

Satellite communication system is actually a kind of microwave communication, it uses the satellite as a relay station ** microwave signal, communication between multiple ground stations, the main purpose of satellite communication is to achieve "seamless" coverage of the ground, because the satellite works in hundreds of thousands, even tens of thousands of kilometers of orbit, so the coverage is much greater than the general mobile communication system.

The development of new satellite communication technologies emerges one after another, such as very small aperture antenna earth station (VSAT) systems, the main features of VSAT networks, simple equipment, small size, low power consumption, and low cost. The installation, maintenance and operation are simple, the degree of integration is high, the intelligent function is strong, and it can be operated unmanned.

The VSAT network also has flexible networking, convenient connection, and strong independence, and is generally used as a private network. The user has control over the network. The network structure is modular, and it is easy to expand and adjust the network structure.

The communication efficiency is high, the performance is high, the reliability is high, the communication capacity can be adapted, and it is suitable for a variety of data rates and a variety of service types.

Satellite communication has the characteristics of long communication distance, high transmission quality, large communication capacity, strong anti-interference ability, good mobility flexibility and high reliability. Since May 1964, when the United States launched the first practical geostationary communications satellite, Intelsat 3, satellite communication technology has advanced with each passing day.

Modern communication requires the use of satellites, mainly because satellites can provide communication services with wide area coverage, and at the same time have the advantages of high-speed transmission and low latency. Satellite communication technology can effectively cover the ocean, vast ground areas and remote areas, which is irreplaceable by land communication. In addition, in sudden disasters, satellite communication technology can also provide fast and accurate emergency rescue services, which has become an indispensable part of modern communication.

Satellite communication technology can achieve more efficient data transmission than traditional communication methods, with the advantages of high-speed transmission and low latency. Compared with traditional terrestrial communication, satellite communication can achieve high-speed data transmission over long distances, and due to the large propagation distance, the use of satellite communication can avoid problems such as signal attenuation caused by long distances. In addition, in satellite communication, the delay of signal transmission is very low, and real-time communication can be realized, which is particularly important in some fields, such as air traffic, military communication, etc.

In addition to providing wide-area coverage and high-speed transmission with low latency, satellite communications can also improve communication efficiency by carrying more data streams. Traditional communication methods have some limitations, because the ability to transmit data is limited, and if the traffic exceeds the limit, it will lead to network congestion. Satellite communication can expand the communication capacity and enhance the flexibility and scalability of communication by carrying multiple parallel data streams, which can meet the application requirements of high-capacity, high-speed and highly integrated information communication.

Generally speaking, the main reason why modern communication uses satellites is because satellite communication has unique advantages such as cross-regional, high-speed, and high-efficiency. Satellite communications can cover all terrestrial areas, such as remote areas, oceans, etc., and also play a very important role in disaster relief and military fields. In addition, satellite communication technology can also provide high-speed, high-efficiency data transmission and carry more data streams to meet the communication needs of different fields.

Therefore, satellite communication technology plays a vital role in all fields of modern communication. <>

Satellite communications and terrestrial microwave communications.

Similarities: both are microwave communications, and they all have the characteristics of microwave communication - they need to be visual, microwave transmission, refraction, and interference.

Differences: 1. Weijian Wangxing communication is approximately ideal free-space microwave transmission, while ground microwave communication is greatly affected by terrain and landform interference;

2. Put the ground microwave relay station in the sky (satellite), it becomes satellite communication, so the transmission distance is not limited by the spherical occlusion of the earth's surface (50 km ground microwave relay). Geostationary orbit satellites can cover about 1 3 area of the Earth's surface (ground-based microwave stations cannot do it);

3. The communication distance has nothing to do with the cost, because within the coverage area of the satellite, any site is connected by satellite. Terrestrial microwaves need to be relayed, and the distance between the two microwave relay stations is generally not more than 50 kilometers;

4. The satellite communication delay is relatively large, the synchronous orbit is about 36,000 kilometers from the ground (equator), and the radio wave delay of single hop (station A-satellite-B station) is seconds, and the double hop is seconds (speed of light = 300,000 kilometers and seconds).

5. The received signal of satellite communication is relatively small, while the ground microwave communication is much stronger. Because of the limited branches of the satellite payload and power supply, as well as the long-distance attenuation from the satellite to the ground (the attenuation of the distance from the satellite to the ground is about 200dB), the satellite signals received by the earth station need to be amplified by low-noise amplifiers first;

6. Satellite communication can be spontaneously self-receiving, and the multiple access mode is flexible: FDMA, TDMA, CDMA, SDMA, and can be freely combined.

The main characteristics of satellite communication are summarized: wide coverage, long transmission distance, cost independent of communication distance, delay time, spontaneous self-collection, flexible multiple access, etc.

I hope it can help you, this information can be found in the now relatively new "Satellite Communication System Engineering".